4.1.1
Angles & Lines
Types of Angle
Types of Angle
There are 4 important types of angle:


Right angle
Right angle
- A right angle is an angle of 90° and is indicated by a square angle marker.


Acute angle
Acute angle
- An acute angle is one that is less than 90°.


Obtuse angle
Obtuse angle
- An obtuse angle is one that is greater than 90° but smaller than 180°.


Reflex angle
Reflex angle
- A reflex angle is greater than 180° but smaller than 360°.
Geometry Basics
Geometry Basics


Vertices and edges
Vertices and edges
- The corners of a polygon are called vertices and the sides are called edges.


Plane
Plane
- A plane is a flat 2 dimensional surface like the surface of a table.


Parallel lines
Parallel lines
- If two lines are parallel they point in exactly the same direction and will never meet.
- Parallel lines are indicated by drawing matching arrows on the lines.
- If there are two different pairs of parallel lines then different arrows are used for each pair.


Perpendicular lines
Perpendicular lines
- Two lines are perpendicular if the angle between them is a right angle.
1Numbers
1.1Integers
1.3Decimals
1.4Powers & Roots
1.5Set Language & Notation
1.6Percentages
1.7Ratio & Proportion
2Equations, Formulae & Identities
2.1Algebraic Manipulation
2.2Expressions & Formulae
2.3Linear Equations
2.4Quadratic Equations
2.5Proportion
3Sequences, Functions & Graphs
3.1Sequences
3.3Graphs
3.4Common Graphs
4Geometry
4.1Angles, Lines & Triangles
4.2Polygons
4.5Circle Properties
4.6Trigonometry & Pythagoras’ theorem
4.7Mensuration of 2D Shapes
4.83D Shapes & Volume
5Vectors & Transformation Geometry
6Statistics & Probability
6.1Statistical Measures
6.2Graphical Representation of Data
Jump to other topics
1Numbers
1.1Integers
1.3Decimals
1.4Powers & Roots
1.5Set Language & Notation
1.6Percentages
1.7Ratio & Proportion
2Equations, Formulae & Identities
2.1Algebraic Manipulation
2.2Expressions & Formulae
2.3Linear Equations
2.4Quadratic Equations
2.5Proportion
3Sequences, Functions & Graphs
3.1Sequences
3.3Graphs
3.4Common Graphs
4Geometry
4.1Angles, Lines & Triangles
4.2Polygons
4.5Circle Properties
4.6Trigonometry & Pythagoras’ theorem
4.7Mensuration of 2D Shapes
4.83D Shapes & Volume
5Vectors & Transformation Geometry
6Statistics & Probability
6.1Statistical Measures
6.2Graphical Representation of Data
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